Field of the Invention
The present invention relates to the field of magnetic resonance imaging, in particular to an image reconstruction method and device for a magnetic resonance imaging system.
Description of the Prior Art
Magnetic resonance imaging (MRI) is an imaging technology involving biomagnetics and nuclear spin that has advanced rapidly with the development of computer technology, electronic circuit technology and superconductor technology. It uses a magnetic field and radio frequency (RF) pulses to induce oscillation of precessing hydrogen nuclei (i.e. H+) in human tissue, so as to generate RF signals that are processed by a computer to form an image. If an object is placed in a magnetic field and irradiated by suitable electromagnetic waves to produce resonance therein, and electromagnetic waves released thereby are then analyzed, it is possible to identify the positions and types of the atomic nuclei of which the object is composed. On this basis, a precise three-dimensional image of the interior of the object can be made. For instance, a moving picture of contiguous slices can be obtained by performing an MRI scan of the human brain, starting at the crown and continuing all the way to the base.
In the field of MRI, parallel imaging techniques have gradually developed from research prototypes into clinical tools. By the spatial arrangement of phased array receiving coils, parallel imaging can accelerate the acquisition of magnetic resonance data, reduce scan times and improve diagnostic functionality. Parallel imaging techniques include the sensitivity encoding (SENSE) technique and simultaneous acquisition of spatial harmonics (SMASH) technique. All parallel imaging techniques require a clear reference line or calibration scan in order to calculate a calibration matrix that represents a receiving coil sensitivity map, this calibration matrix then being used in a subsequent image reconstruction process.
FIG. 1 is a schematic diagram of the processing involved in an MRI clinical examination in the prior art. As FIG. 1 shows, first a localizer scan (L) is performed, followed by a first scan protocol (P1), a second scan protocol (P2), a third scan protocol (P3) and a fourth scan protocol (P4) in sequence. Each scan protocol comprises a step (C) of calculating a receiving coil calibration matrix and a step (PA) of parallel acquisition of data. In step (C), the calibration data can be divided into assumed missing data and surrounding data of assumed missing data, and the receiving coil calibration matrix can then be calculated according to the assumed missing data and surrounding data of assumed missing data.
There are generally multiple scan protocols; if a receiving coil calibration matrix is calculated for every scan protocol, there will be a significant amount of calculation to be done, and working efficiency will be reduced.